The invention relates to check valves of the variety in which plural like valve members are hinged at essentially a single radial plane in an annular valve body, for independent coaction with seat-post structure which may be secured to or formed integrally with the valve body.
In all such check valves known to me, the design philosophy is to provide the seat post structure for all valve members in essentially a single radial plane of the valve body, said plane being essentially in or slightly offset upstream from the radial plane of hinge action. It is an unavoidable consequence of such design philosophy that seat-post structure will locally reduce the open cross-sectional area available for fluid flow, and that valve-member motion between open and closed positions will be in the order of 90 degrees, unless up-stop measures are adopted to assure smaller displacements, thus further contributing to local restriction of the flow-handling capacity of the valve. Such large valve-member displacements can account for seating impacts of such severity as to materially reduce the expected service life of the valve.